Authentication of turmeric powder using hyperspectral Raman system

Abstract

Turmeric powder (Curcuma longa L.) is known for its use in foods, in medicine, and as a cosmetic. In recent years, economically driven contamination of turmeric powder with different chemicals is increasing. This study used a 1064 nm hyperspectral Raman imaging system for detection of Sudan Red G dye contamination in turmeric powder. Sudan Red was mixed with turmeric powder at five concentration levels (1%, 5%, 10%, 15%, and 20%- w/w). Each mixture sample was packed in a sample container. A Raman chemical image of each sample was acquired across the 7.5 mm x 7.5 mm surface area using a 0.25 mm step size. The spectral fingerprint of turmeric and Sudan Red were identified and used to obtain a binary image from the Raman chemical image of each sample. A simple threshold method was applied to convert the contaminant pixels into white pixels and turmeric pixels into the black (background) pixels. The detected Sudan Red pixels were correlated with the actual concentration in the sample. The result shows that the Sudan Red pixels in the sample image is linearly correlated (R2 = 0.99) with the actual concentration of the sample. This study demonstrated the 1064 nm hyperspectral Raman imaging system as a potential tool to detect chemical contaminants in turmeric powder.